Rotary internal combustion engine with low starting drag

ABSTRACT

A rotary internal combustion engine having provision to eliminate the oil pump drag during low temperature starting by means of a slip-clutch cutting out the oil pump during conditions of high oil viscosity, and having bearings capable of running with only residual lubrication and without additional lubricant supply until the engine warms up.

* nited States Patent Jones 1 1 Jan. 23, 1973 15 1 ROTARY INTERNAL COMBUSTION 2,049,794 8/1936 Armor ..418/88 ENGINE WITH ow STARTING DRAG 3,359,952 12/1967 Jones et ..418/88 3,398,886 8/1968 Roach ..4l8/88 [75] Inventor: Charles Jones, l-lillsdale, NJ.

[73] Assignee: Curtiss-Wright Corporation Primary Examiner-C H1153! Attorney-Raymond P. Wallace et al. [22] Filed: Nov. 8, 1971 211 App]. No.: 196,634 A S ACT A rotary internal combustion engine having provision [52] US. Cl. ..4l8/88, 418/84, 123/809, {0 eliminate th il pump drag during low temperature 184/27 R, 192/41 5 starting by means of a slip-clutch cutting out the oil 51 Int. Cl ..F02n 15/00 p p during conditions of high Oil viscosity, and [58] Field of Search ..418/81, 84, 88; 123/809; ing bearings capable of running with only residual 184/27, 31, 36 lubrication and without additional lubricant supply until the engine warms up. 56 R l Ct d i l e erences I e 5 Claims, 2 Drawing Figures UNlTED STATES PATENTS 1,640,472 8/1927 Starkey ..l92/4l S PATENTEDJAH 23 I975 SHEET 1 OF 2 INVENTOR.

9/4/9155 JOIV$ BY W PATENTEDJMI'ZS I975 3.712.766

SHEET 2 0F 2 INVENTOR.

CHARLES JONES AGENT ROTARY INTERNAL COMBUSTION ENGINE WITI-I LOW STARTING DRAG BACKGROUND OF THE INVENTION This invention relates to rotary internal combustion engines, and more particularly to small engines of this type wherein hand starting may be utilized, or which have electric starters of low power or wherein the battery at low temperatures will not put out a high current.

Such small engines are used for small vehicles, garden tractors, lawnmowers, snowmobiles, snowblowers, and light marine and industrial applications. They are commonly air cooled, but may have an oil pump for internal oil cooling of the rotor and for supplying lubricating oil, in which case they are generally provided with sleeve bearings. When such an engine is cold, particularly during cold weather as may be the case with snowmobiles and snowblowers, the oil is very viscous, requiring a pumping effort which is of the order of ten times as high as that required for oil at normal operating temperature. The sleeve bearing, with its hydrodynamic action, also presents great resistance when the oil is cold. These factors make it difficult to start engines of this class, and the high drag of cold, viscous oil may also cause stalling during the first few moments of running.

SUM MARY In the present invention such problems are overcome by the use of slip arrangement which declutches the oil pump during conditions of high oil viscosity, and by the use of rolling contact bearings which avoid the high drag resistance of hydrodynamic bearings, and which also have the ability to run temporarily without feeding lubrication, which will be a natural consequence of cutting out the oil pump. Further, operating during the initial few minutes without supplying cooling oil to the interior of the rotor results in a faster warm-up.

It is therefore an object of this invention to provide means for easy starting of a cold rotary engine.

It is another object to provide self-operating means of decoupling the oil pump of a rotary engine during conditions of low temperature and high oil viscosity and recoupling the pump when operating temperature and low oil viscosity are reached.

Other objects and advantages will become apparent on reading the following specification in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section along the axis of a rotary engine embodying the invention, and

FIG. 2 is a sectional view of a clutch mechanism for driving the oil pump.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a cross-section of an air cooled rotary engine having an oil cooled rotor. The side walls 11 and 12 of the housing are provided with fins for air cooling in that region of the engine where heat is to be dissipated, as is also the peripheral wall 13. A shaft 14 transpierces the side walls and bears an eccentric portion 16 within the housing cavity, on which is rotatably mounted a hollow rotor 17 having a circular aperture 20 adjacent to housing side wall 12 and communicating with the interior of the rotor.

The shaft 14 turns in rolling contact bearings 18 and 19 borne by the side walls of the housing, and the rotor turns on rolling contact bearing 21 mounted on the eccentric. A fixed spur gear 22 is mounted on side wall 11, in mesh with a ring gear 23 borne by the rotor, the two gears assisting in maintaining the requisite speed ratio between the rotor and the shaft.

For the purpose of providing oil for the various bearings and for internal cooling of the rotor there is provided an oil sump 24, and a rotary oil pump 26 driven by the shaft. The pump intake at 27 communicates by appropriate passage means with the oil sump 24, and the pump discharges through a jet passage 28 into the interior of the hollow rotor, the orifice of passage 28 being positioned at such radial distance from the shaft axis that its discharge will always be within the periphery of the rotor opening 20.

The eccentric 16 is hollow in the crescent-shaped portion 29 which has the greatest radial extent from the axis of shaft 14, and has an internal rib member 31 having an aperture 32 therethrough. At each revolution of the eccentric, aperture 32 traverses a position generally in register with the oil emerging from the orifice of jet 28, so that a portion of the oil squirts through the rib aperture 32 to lubricate the gears 22 and 23. The hollow portion of the eccentric has also, on the side adjacent to the oil jet 28, an internally extending lip 33 which forms a channel 34 with the internal rib 31. A bore 36 extends between the channel 34 and the other peripheral surface of the eccentric to the seat of bearing 21, and oil collected in channel 34 is impelled outwardly by centrifugal force through bore 36 to lubricate bearing 21. The remainder of the oil pumped through jet 28 is distributed around the rotor during the revolution thereof, where it serves as a coolant to control rotor temperature. The interior of the rotor is in communication with bearing 18, so that this bearing receives lubricant therefrom; bearing 19 is in communication with the rotor interior through the inner diameter of spur gear 22, and thus receives lubrication. All the oil eventually drains through bores 37 and 38 in the side walls into spaces 39 and 41, whence it returns by appropriate channeling (not shown) to the oil sump for recirculation.

The pump mechanism 26 may be of any type suitable for rotary drive, and is positioned surrounding the shaft in an appropriately formed shell 42 abutting a boss 43 extending from the side wall 12. Axial positioning of the pump assembly is accomplished by a spacer sleeve 44 surrounding the shaft between the pump and the bearing 18 is mounted in the side wall 12, and by another spacer sleeve 46 at the outer end of the pump assembly, held in position by the counterweight 47 attached to the shaft. A seal 45 precludes loss of oil from the outer end of the pump assembly.

As will be more readily seen in FIG. 2,' the pump is driven by a slip clutch mechanism 48. By way of example there is shown a clutch of the type wherein a helical spring is engaged by friction at its outer periphery with the inner diameter of the .pump members, the spring being appropriately keyed to the shaft so that it rotates therewith. The degree of frictional engagement between the slip clutch and the pump is selected for operating the pump at normal engine temperature and oil viscosity, and slips when the oil is too cold and viscous to pump readily. Thus, when starting the engine at low ambient temperatures the pump does not operate, but the shaft load caused by the slipping clutch is only that which would be required to pump oil at operating viscosity. Hence the cranking effort is not so great as to cause difficulty in starting.

The jet orifice 28 through which oil is discharged is appropriately sized for the desired amount of oil at a given pump pressure, which is well within the operating range of the pump. The pump outlet is provided with the conventional pressure relief valve and bypass line (not shown), by means of which pressure is to the sump.

Although only one type of slip clutch is shown by way of illustration, it will be understood that other types are suitable, such as a spring-loaded plate clutch, or a series of O-rings on the shaft in frictional engagement with the pump.

The ball bearings and roller bearings shown, being of rolling contact type, are superior to sleeve bearings in their ability to run for limited start-up periods on residual lubricant, without additional supply from the pump. However, with proper bearing design and clearances, sleeve bearings can also be operated in this manner for a short time, that is, at low speed and no load, such as at start-up.

What is claimed is:

1. A rotary engine having a pair of parallel side walls spaced apart by a peripheral wall defining an engine cavity, a shaft transpiercing the side walls and turning in bearings borne by the side walls and having an eccentric portion within the engine cavity, the eccentric portion being surrounded by a bearing and having a hollow rotor rotatably mounted thereon, one of the side walls having a fixed spur gear mounted thereon within the engine cavity, the rotor having an internal gear in mesh with the spur gear, an oil sump for cooling and lubrication oil disposed externally to the engine cavity, an oil pump disposed externally to the engine cavity and driven by the shaft and having an intake in communication with the oil sump, one of the side walls having passage means therethrough with one end of the passage communicating with the pump discharge and the other end communicating with the engine cavity for supplying lubricating and cooling oil thereto, slip clutch means disposed between the shaft and the pump and providing frictional engagement therebetween, the degree of frictional engagement being such that the shaft drives the pump to pump oil at normal engine operating temperature and oil viscosity and such that the clutch means slips at low engine temperature and high oil viscosity and the pump does not operate.

2. The combination recited in claim 1, wherein on the side adjacent to the pump discharge orifice the rotor has a circular aperture communicating with the hollow interior, and the pump discharge orifice is positioned at such radial distance from the shaft axis that the orifice will be within the periphery of the rotor aperture at all rotor positions so that the interior of the rotor receives a constant supply of cooling oil.

3. The combination recited in claim 2, wherein the spur gear and the internal gear are disposed at the axially opposite side of the engine cavity from the pump orifice, and that portion 0 the eccentric having the greatest radial extent from the shaft axis has passage means therethrough which comes in register with the pump orifice at each revolution of the eccentric, so that the oil jet emerging from the pump orifice squirts through the eccentric passage to lubricate the spur gear and the internal gear.

4. The combination recited in claim 3, wherein that portion of the eccentric having the greatest radial extent from the shaft axis has an arcuate internal channel open radially inwardly and communicating with the rotor interior, and passage means communicating between the internal channel and the bearing surrounding the eccentric so that oil collecting in the internal channel of the eccentric is impelled outwardly by centrifugal force through the passage to the eccentric bearing.

5. The combination recited in claim 4, wherein the shaft bearings borne by the side walls are in communication with the rotor interior and receive lubricating oil therefrom.

' mm sures PATENT ohm 3s QER'III IQA'I'E RRETIN Patent No. 3, 712 766 D t d January 23, 1973 Inventor (s) Charles Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

I Column 2 line 31, the word "other" should read outer Column 3, line 14, after the word is" insert the follow- I ing words which were left out: -maintained at: the desired value, and any excess of oil is returned-.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-IOSO (10-69) UsCOMM-DC 60376-F'69 u.s. eovznuuzm PRINTING ornc: was o--3s6-334.

' mm sures PATENT ohm 3s QER'III IQA'I'E RRETIN Patent No. 3, 712 766 D t d January 23, 1973 Inventor (s) Charles Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

I Column 2 line 31, the word "other" should read outer Column 3, line 14, after the word is" insert the follow- I ing words which were left out: -maintained at: the desired value, and any excess of oil is returned-.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-IOSO (10-69) UsCOMM-DC 60376-F'69 u.s. eovznuuzm PRINTING ornc: was o--3s6-334.

"mm? STATES PATENT eTTT-TJT @ER'I'IFICATE @II @QRREQTIUN Patent No. 3, 712 766 Dated January 23 1973 Invento g) Charles Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

' Column 2, line 31, the Word "other" should read -outer--.

Colurn 3, line 14 after the word "'is insert the following words which were left out: -maintained at" the desired value, and any excess of oil is returned-.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. 7 ROBERT GOTTSCHALK Attesting Officer 7 Commissioner of Patents 1 FORM PO-105O (10-69) USCOMM-DC 5375-P69 Y UTS. GOVERNMENT PRINTING OFFICE: [959 0-365-334, 

1. A rotary engine having a pair of parallel side walls spaced apart by a peripheral wall defining an engine cavity, a shaft transpiercing the side walls and turning in bearings borne by the side walls and having an eccentric portion within the engine cavity, the eccentric portion being surrounded by a bearing and having a hollow rotor rotatably mounted thereon, one of the side walls having a fixed spur gear mounted thereon within the engine cavity, the rotor having an internal gear in mesh with the spur gear, an oil sump for cooling and lubrication oil disposed externally to the engine cavity, an oil pump disposed externally to the engine cavity and driven by the shaft and having an intake in communication with the oil sump, one of the side walls having passage means therethrough with one end of the passage communicating with the pump discharge and the other end communicating with the engine cavity for supplying lubricating and cooling oil thereto, slip clutch means disposed between the shaft and the pump and providing frictional engagement therebetween, the degree of frictional engagement being such that the shaft drives the pump to pump oil at normal engine operating temperature and oil viscosity and such that the clutch means slips at low engine temperature and high oil viscosity and the pump does not operate.
 2. The combination recited in claim 1, wherein on the side adjacent to the pump discharge orifice the rotor has a circular aperture communicating with the hollow interior, and the pump discharge orifice is positioned at such radial distance from the shaft axis that the orifice will be within the periphery of the rotor aperture at all rotor positions so that the interior of the rotor receives a constant supply of cooling oil.
 3. The combination recited in claim 2, wherein the spur gear and the internal gear are disposed at the axially opposite side of the engine cavity from the pump orifice, and that portion of the eccentric having the greatest radial extent from the shaft axis has passage means therethrough which comes in register with the pump orifice at each revolution of the eccentric, so that the oil jet emerging from the pump orifice squirts through the eccentric passage to lubricate the spur gear and the internal gear.
 4. The combination recited in claim 3, wherein that portion of the eccentric having the greatest radial extent from the shaft axis has an arcuate internal channel open radially inwardly and communicating with the rotor interior, and passage means communicating between the internal channel and the bearing surrounding the eccentric so that oil collecting in the internal channel of the eccentric is impelled outwardly by centrifugal force through the passage to the eccentric bearing.
 5. The combination recited in claim 4, wherein the shaft bearings borne by the side walls are in communication with the rotor interior and receive lubricating oil therefrom. 